CPLD-driven IGBT short-circuit current dynamic monitoring method and system

Abstract

The invention discloses a CPLD-driven IGBT short-circuit current dynamic monitoring method and system, and relates to the technical field of power electronics, and the method comprises the specific steps of S100 real-time data acquisition, S200 dynamic threshold calculation, S300 short-circuit state judgment, S400 rapid protection execution, and S500 fault data recording and uploading. Accurate and prospective judgment of the short circuit state of the IGBT is achieved, two stress parameters including the direct-current bus voltage and the junction temperature serve as independent variables, when the bus voltage rises, the voltage stress borne by the IGBT in the turn-off period is increased, meanwhile, the current peak at the short circuit moment is more remarkable, early warning is conducted in advance by dynamically lowering the threshold value, and therefore the short circuit state of the IGBT is accurately judged. According to the mechanism, the monitoring system does not simply respond to the occurred overcurrent, but can pre-judge the safety boundary of the device under the current working condition, so that intervention is implemented before the current really reaches a dangerous peak value, and a protection blind area under a severe working condition is effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a method and system for dynamic monitoring of short-circuit current of IGBTs driven by CPLD. Background Technology

[0002] As the core power conversion device in new energy power generation systems such as wind and solar power, the reliability of power electronic converters directly affects the stability and efficiency of the entire power generation system. Insulated gate bipolar transistors (IGBTs) are key actuators in the power unit of the converter, operating under harsh conditions of high voltage, high current, and high-frequency switching. In actual operation, IGBTs may instantly enter a short-circuit state due to sudden load changes, insulation aging, or abnormal drive, generating huge currents far exceeding the rated value. If protective shutdown cannot be performed in a very short time, the IGBT will suffer irreversible and permanent damage under huge thermal and electrical stress, causing the entire converter to shut down, resulting in huge economic losses and maintenance costs. Therefore, rapid and accurate monitoring and protection of IGBT short-circuit current is the primary technical challenge to ensure the safe and reliable operation of high-power power electronic devices.

[0003] Currently, existing IGBT short-circuit protection schemes mainly rely on a combination of hardware detection circuits and software algorithms of digital signal processors. Hardware circuits typically determine overcurrent through desaturation detection, but their detection thresholds are usually fixed or only have simple temperature compensation, and cannot adaptively adjust according to dynamic operating conditions such as DC bus voltage fluctuations and device aging. In complex application scenarios, false protection or protection delays are prone to occur. On the other hand, DSP-based software protection strategies are limited by their sequential execution architecture and interrupt response delay. The overall response time from sampling and calculation to finally issuing the shutdown command is long, which makes it difficult to meet the requirements of modern high-power IGBTs for extreme speed.

[0004] In summary, existing technologies cannot provide rapid protection against IGBT short-circuit faults in complex operating conditions and highly reliable environments such as wind farms and energy storage stations. Therefore, there is an urgent need for a technology that deeply integrates high-speed hardware response with intelligent algorithm decision-making to fundamentally improve the inherent reliability and ease of operation and maintenance of power units. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a dynamic monitoring method and system for IGBT short-circuit current driven by CPLD. It introduces a dynamic threshold algorithm based on a thermo-electric coupling model, which enables accurate and forward-looking judgment of IGBT short-circuit state. By using the two stress parameters, DC bus voltage and junction temperature, as independent variables, when the bus voltage increases, the voltage stress borne by the IGBT during turn-off increases, and the current spike at the moment of short circuit is also more significant. By dynamically lowering the threshold to provide early warning, this mechanism enables the monitoring system to no longer simply respond to overcurrent that has occurred, but to predict the safety boundary of the device under the current operating conditions, thereby intervening before the current actually reaches the dangerous peak value, effectively avoiding protection blind spots under harsh operating conditions and malfunctions under mild operating conditions.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: On the one hand, a method for dynamic monitoring of short-circuit current of IGBT driven by a CPLD, the specific steps of which are as follows:

[0007] S100 Real-time Data Acquisition: The data acquisition module controlled by the CPLD acquires the collector current flowing through the IGBT in real time. Collector-emitter voltage of IGBT and the junction temperature of IGBT ;

[0008] S200, Dynamic Threshold Calculation: The CPLD is based on the real-time acquired DC bus voltage. and the junction temperature of the IGBT Dynamically calculate and adjust the short-circuit current judgment threshold. ;

[0009] S300, Short-circuit condition judgment: The CPLD will collect the collector current in real time. With the dynamic short-circuit current threshold Compare and simultaneously analyze the collector-emitter voltage. rate of change When preset conditions are met, the IGBT is determined to be in a short-circuit state;

[0010] S400, Fast Protection Execution: After determining that a short circuit is detected, the CPLD directly generates and outputs a turn-off signal to the IGBT drive circuit to force the IGBT to perform a soft turn-off operation.

[0011] S500, Fault Data Recording and Uploading: The CPLD records the timestamp of the short-circuit fault, the fault type, and the key electrical parameters at the time of the fault. It uploads the fault data through the communication interface and initiates self-diagnosis and recovery.

[0012] Furthermore, the specific steps for real-time data acquisition in S100 are as follows:

[0013] The CPLD has a built-in fixed-frequency 500kHz sampling clock. The CPLD controls a multi-channel analog-to-digital converter to synchronously acquire data via a parallel bus. , and The first channel acquires the analog voltage signal output by the current sensor, and the second channel acquires the signal after isolation by the high-voltage differential probe. The signal, acquired via the third channel after voltage division from the DC bus, is... Signal;

[0014] The CPLD internally allocates a double-buffered RAM area for temporarily storing sampled data and calculating the current differential value at each sampling point in real time. and voltage change rate This is used for subsequent short-circuit detection, reducing the computational burden on the main control DSP.

[0015] Furthermore, in S200, the CPLD calculates the short-circuit current judgment threshold through multi-parameter coupling. ,in, It is a dynamically calculated short-circuit current threshold, which serves as a benchmark value for real-time judgment of short-circuit conditions. It is the reference short-circuit current threshold under rated operating conditions, corresponding to the maximum permissible short-circuit current at rated DC voltage and rated junction temperature. This is the rated DC bus voltage, with a default value of 1050V-1400V. The DC bus voltage is collected in real time, sampled by a voltage sensor, converted by an analog-to-digital converter, and then input to the CPLD. This is a voltage correction factor, ranging from 0.8 to 1.2, used to characterize the effect of DC voltage on the IGBT's saturation voltage drop and short-circuit capability. For real-time monitoring of IGBT junction temperature, This is the rated operating junction temperature of the IGBT, with a default value of 125°C-150°C. When the DC voltage increases, the short-circuit current capability of the IGBT decreases, so the threshold needs to be adjusted in the opposite direction. When the junction temperature increases, the current carrying capacity and withstand time of the IGBT decrease, so the threshold needs to be reduced exponentially, thereby achieving dynamic adaptive protection and avoiding false triggering or insufficient protection under high voltage and high temperature conditions.

[0016] Furthermore, in S300, the preset condition for the short-circuit state is:

[0017] when When it enters a short circuit state, among which, It is a preset voltage change rate threshold. for rate of change and , This represents the collector-emitter voltage at the current sampling moment. This represents the voltage at the previous sampling time. The sampling interval is denoted as .

[0018] Furthermore, in S500, the self-diagnosis and recovery process is as follows:

[0019] A self-test trigger pulse is generated by the CPLD to initiate a comprehensive self-diagnostic sequence, which includes sensor path verification, drive power monitoring and CPLD logic self-test.

[0020] For sensor path verification: The CPLD outputs a standard analog test signal and injects it into the front end of the current and voltage sampling channels to check whether the reading returned by the ADC is within the error range. If the deviation exceeds the limit, the sensor is marked as faulty and the backup channel is switched to trigger an alarm.

[0021] For drive power monitoring: The CPLD monitors the auxiliary power supply voltage of the IGBT driver board through the analog-to-digital converter. When the voltage value exceeds the standard value by 5%, it is judged that the drive power supply is abnormal, the PWM output is immediately blocked and the power fault code is recorded.

[0022] For CPLD logic self-testing: The CPLD runs the built-in BIST logic to test the integrity of the internal registers, state machine and memory. By comparing the test vectors and expected outputs, the normal logic function is verified.

[0023] Status reporting mechanism: All self-diagnostic results and recovery operations are recorded in memory and uploaded in real time via a communication interface for operation and maintenance analysis and predictive maintenance.

[0024] On the other hand, the CPLD-driven IGBT short-circuit current dynamic monitoring system comprises the following components:

[0025] The CPLD main control module, as the system's logic processing unit, internally implements functions including ADC control, dynamic threshold calculation, short-circuit state judgment state machine, and protection signal generation through hardware description language programming.

[0026] The multi-parameter sampling module, connected to the CPLD main control module, is used to acquire the collector current of the IGBT. Collector-emitter voltage and DC bus voltage ;

[0027] The temperature monitoring module, connected to the CPLD main control module, is used to monitor the junction temperature of the IGBT in real time. ;

[0028] The IGBT drive and protection circuit is connected to the CPLD main control module and the gate of the IGBT. It is used to receive the normal PWM signal and the shutdown protection signal sent by the CPLD, and drive the IGBT to perform the corresponding switching action.

[0029] The communication interface module is connected to the CPLD main control module and is used to realize data interaction between the CPLD main control module and the external main control DSP or host computer.

[0030] Furthermore, the working process of the IGBT drive and protection circuit is as follows:

[0031] Driver chip: IGBT driver chip is used to provide isolation, amplification and protection functions. The operating voltage is +15V / -8V and the peak output current is ≥10A to ensure fast switching and Miller effect suppression.

[0032] Soft shutdown circuit design: After receiving the protection signal from the CPLD, the drive circuit starts the soft shutdown sequence. Through a controllable gate resistor network, the gate voltage is slowly reduced from +15V to -8V, and the drop time is controlled within 2-5 microseconds to suppress shutdown overvoltage and voltage spikes.

[0033] Active clamping unit: The circuit integrates active clamping function, which is achieved through a TVS diode and a feedback loop when... When the voltage exceeds the preset clamping voltage of 1200V, current is automatically injected into the gate to limit the voltage rise and protect the IGBT from overvoltage breakdown.

[0034] Status feedback mechanism: The drive circuit monitors the saturation voltage drop and gate state of the IGBT in real time, and feeds these status signals back to the CPLD through optocoupler isolation to form a closed-loop control. The CPLD adjusts the drive parameters according to the feedback.

[0035] Furthermore, the communication interface module includes:

[0036] Physical layer interface: Provides a variety of physical interface options, including high-speed fiber optic interface, CAN bus interface and SPI serial interface;

[0037] Protocol stack architecture: The CPLD has a built-in communication protocol stack, including physical layer encoding / decoding, data link layer frame verification, and application layer message parsing. The application layer message is defined as: header byte, command word, data field, and tail byte.

[0038] Configuration and diagnostic functions: Through the communication interface, the host computer can remotely configure the parameters of the CPLD and read the system self-diagnostic logs to achieve remote monitoring and maintenance;

[0039] Redundancy design: The communication link supports dual redundancy mode. When the main channel fails, it automatically switches to the backup channel, and all communication data is backed up and stored in the CPLD to prevent data loss.

[0040] Compared with existing technologies, the CPLD-driven IGBT short-circuit current dynamic monitoring method and system have the following advantages:

[0041] This invention introduces a dynamic threshold algorithm based on a thermo-electric coupling model, enabling accurate and forward-looking judgment of IGBT short-circuit states. By using the DC bus voltage and junction temperature as two stress parameters as independent variables, when the bus voltage increases, the voltage stress borne by the IGBT during turn-off increases, and the current spike at the moment of short circuit becomes more significant. By dynamically lowering the threshold to provide early warning, this mechanism allows the monitoring system to no longer simply respond to overcurrent that has already occurred, but to predict the safety boundary of the device under the current operating conditions, thereby intervening before the current actually reaches the dangerous peak value. This effectively avoids protection blind spots under harsh operating conditions and malfunctions under mild operating conditions.

[0042] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0044] Figure 1 The operation flowchart of the dynamic monitoring method for short-circuit current of IGBT driven by CPLD;

[0045] Figure 2 A step-by-step diagram of a method for dynamically monitoring the short-circuit current of an IGBT driven by a CPLD. Detailed Implementation

[0046] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0047] Example 1

[0048] This embodiment provides a complete workflow for a CPLD-driven IGBT short-circuit current dynamic monitoring method. This method uses a CPLD as the core control unit, collects key electrical and temperature parameters of the IGBT in real time, accurately determines the short-circuit state by combining a dynamic threshold algorithm, and then executes protection operations and records fault data with hardware-level response speed. This effectively solves the problems of fixed threshold and response delay in existing solutions and is suitable for the safety protection of IGBTs in high-power power electronics scenarios such as new energy power generation and energy storage.

[0049] First, the real-time data acquisition phase (S100) begins. In this phase, the CPLD controls the multi-channel data acquisition module to synchronously acquire key parameters of the IGBT during operation, providing data support for subsequent judgment and calculation. The CPLD is pre-configured with a fixed sampling clock of 500kHz, which serves as the synchronization reference for data acquisition, ensuring consistent sampling times for all parameters and avoiding data analysis errors caused by time differences. Driven by the sampling clock, the CPLD sends control signals to the multi-channel analog-to-digital converter (ADC) via a parallel bus to initiate the synchronous sampling process. The first channel of the ADC specifically acquires the analog voltage signal output by the current sensor. This analog signal is correlated with the collector current flowing through the IGBT. The two channels exhibit a linear correlation, with the second channel acquiring the IGBT collector-emitter voltage after processing by the high-voltage differential probe. The high-voltage differential probe can effectively isolate high-voltage interference and ensure signal transmission. The accuracy and security of the signal; the third channel acquires the voltage signal of the DC bus after it has been processed by the voltage divider circuit, i.e., the DC bus voltage. The voltage divider circuit can reduce high-voltage signals to the range of the ADC, preventing damage to the acquisition device. Meanwhile, the CPLD internally has a double-buffered RAM area for temporarily storing the signals obtained from each sample. , and Data. The dual-buffered design enables parallel operations of data acquisition, storage, and computation. While one buffer stores the current sampled data, the other buffer can simultaneously be used by the CPLD to read data and perform calculations, preventing data loss or acquisition interruption. The CPLD also calculates the differential current value at each sampling point in real time based on the continuously sampled data stored in the dual-buffered RAM area. and voltage change rate The specific calculation method is to divide the parameter difference between two adjacent sampling times by the sampling interval. It is concluded that these dynamically changing parameters will serve as an important basis for subsequent short-circuit state judgment, and the entire data acquisition and preliminary calculation process is completed by CPLD hardware logic without relying on external main control DSP, which greatly reduces the computational burden of DSP.

[0050] Then, the dynamic threshold calculation stage (S200) begins. In this stage, the CPLD calculates the threshold based on the data collected in stage S100. and IGBT junction temperature The dynamic threshold for judging short-circuit current is calculated using a multi-parameter coupling formula. This allows the threshold to adapt to the current operating conditions, avoiding misjudgment or insufficient protection under complex operating conditions due to a fixed threshold, and enabling real-time acquisition of the IGBT junction temperature. This temperature data is consistent with the data collected in S100. Together with the input parameters of the formula, the formula used for dynamic threshold calculation is as follows: ,in, It is the preset reference short-circuit current threshold under rated operating conditions, corresponding to the IGBT at rated DC voltage. and rated junction temperature The maximum permissible short-circuit current is the basic benchmark value for threshold calculation; This refers to the rated DC bus voltage of the IGBT. The actual DC bus voltage is collected in real time in S100; This is a voltage correction factor used to characterize the effect of DC voltage on the saturation voltage drop and short-circuit capability of IGBTs. Its value needs to be preset according to the device characteristics and application scenarios of IGBTs. This refers to the rated operating junction temperature of the IGBT. The junction temperature influence coefficient is calculated based on real-time data from the CPLD. With Rated The ratio, combined with Calculate the voltage correction term ,when As the value increases, the correction term decreases, resulting in Reduce the current to match the reduced short-circuit current capability of the IGBT under high voltage; then adjust according to real-time... With Rated The difference is expressed by an exponential function. Calculate the junction temperature correction term when As the value increases, the value of the exponential function decreases exponentially, further reducing... To adapt to the reduced current carrying capacity and withstand time of IGBTs as junction temperature increases, CPLDs will... Multiplying by the voltage correction term and the junction temperature correction term yields the dynamic short-circuit current threshold under the current operating condition. The threshold is then temporarily stored in an internal register for later short-circuit detection.

[0051] Next, the short-circuit condition determination stage (S300) begins. In this stage, the CPLD combines the real-time data collected by S100. and calculation The dynamic threshold obtained from S200 Comparative analysis is performed to determine whether the IGBT has entered a short-circuit state. The CPLD reads the dynamic threshold from its internal register. Simultaneously, the latest real-time collector current is retrieved from the double-buffered RAM area. The two are compared in real time to determine... Is it greater than At the same time, the CPLD will call the pre-calculated values ​​from the S100 stage. rate of change Its calculation method is as follows ,in, This represents the collector-emitter voltage at the current sampling moment. For the previous sampling time , The sampling interval, i.e., the period corresponding to a 500kHz sampling clock, is calculated in real time by the CPLD. Compared with the preset voltage change rate threshold Compare and judge Is it greater than The determination of a short circuit state requires the simultaneous fulfillment of two preset conditions: one is the real-time collector current. Secondly rate of change The CPLD will only determine that the IGBT has entered a short-circuit state when both conditions are met simultaneously. This dual-condition judgment mechanism can effectively eliminate false judgments caused by a single parameter anomaly. For example, when... Briefly exceeded the threshold but Under normal circumstances, the problem might be load fluctuations rather than a short circuit, in which case the protection will not be triggered; however, when a short circuit occurs, not only... It will rapidly exceed the threshold. It can also change rapidly due to abnormal device conduction status, satisfying dual-condition trigger protection and ensuring the accuracy of judgment.

[0052] Secondly, in the fast protection execution phase (S400), the CPLD immediately generates and outputs a turn-off signal the instant it determines that the IGBT has entered a short-circuit state. This drives the IGBT to perform a soft turn-off operation, preventing damage to the device caused by prolonged high current. Since the CPLD uses hardware logic to execute the judgment and signal generation, there is no need for sequential execution of software instructions. The response time from short-circuit determination to outputting the turn-off signal can be controlled in the microsecond range, meeting the IGBT's speed requirement for short-circuit protection. The turn-off signal generated by the CPLD is directly sent to the IGBT's drive circuit. Upon receiving the signal, the drive circuit immediately starts the preset soft turn-off sequence. The soft turn-off sequence is controlled by a gate resistor network. The specific process is as follows: The drive circuit first slowly reduces the forward voltage of the IGBT gate from +15V during normal conduction. The rate of reduction is controlled by the resistance value of the gate resistor to avoid turn-off overvoltage caused by a sudden voltage drop. When the gate voltage drops to near 0V, it is further reduced to the reverse bias voltage -8V to ensure reliable IGBT turn-off and prevent re-conduction. The voltage drop time of the entire soft turn-off process needs to be preset according to the IGBT device parameters and is achieved by controlling the resistance value of the gate resistor network. The ultimate goal is to suppress overvoltage and voltage spikes generated during the turn-off process and protect the IGBT from electrical stress damage. At the same time, the active clamping unit in the drive circuit monitors the IGBT in real time. ,when When the preset clamping voltage is exceeded, the active clamping unit automatically injects current into the IGBT gate through the TVS diode and feedback loop to adjust the gate potential, thereby limiting the clamping voltage. To prevent the IGBT from being damaged by overvoltage breakdown, the voltage drop is further increased. In addition, the drive circuit will feed back information such as the IGBT's saturation voltage drop and gate state to the CPLD through optocoupler isolation, forming a closed-loop control. The CPLD can determine whether the protection operation is being performed normally based on the feedback information. If an abnormality is detected, further emergency blocking measures will be taken.

[0053] Finally, the fault data recording and uploading stage (S500) begins. After the IGBT completes its soft shutdown protection, the CPLD records the short-circuit fault-related data and initiates a self-diagnosis and recovery process to support subsequent fault analysis and system maintenance, while ensuring the system can resume normal operation after the fault is resolved. First, the CPLD records the timestamp of the short-circuit fault occurrence, provided by its internal real-time clock module, accurate to the microsecond level, to pinpoint the exact moment the fault occurred. Second, it records the fault type based on the parameter characteristics at the time of the short circuit. Exceeding the limit, The changing trend is used to determine whether the fault is an overload short circuit, an abnormal gate drive short circuit, or a sudden load change short circuit, etc. Key electrical parameters at the time of the fault are recorded, including the instantaneous values ​​at the moment of the fault. , , and Numerical values ​​and parameter change curves before and after the fault are retrieved and stored from the double-buffered RAM area. After the fault data is recorded, the CPLD uploads the data to the external main control DSP or host computer through the communication interface. The communication interface supports multiple physical interfaces such as high-speed fiber optic interface, CAN bus interface or SPI serial interface. The CPLD can select the corresponding interface for data transmission according to the system configuration. During data transmission, the CPLD's built-in communication protocol stack processes the data, including physical layer encoding / decoding, data link layer frame verification and application layer message parsing. The application layer message adopts a structure of header byte, command word, data field and tail byte. The header byte is used to identify the start of the message, the command word is used to describe the data type, the data field stores the specific fault parameters, and the tail byte is used to identify the end of the message to ensure the accuracy and integrity of data transmission. Simultaneously with data upload, the CPLD initiates a self-diagnosis and recovery process. The CPLD generates a self-test trigger pulse, initiating a comprehensive self-diagnosis sequence, which includes three parts: sensor path verification, drive power monitoring, and CPLD logic self-test. In sensor path verification, the CPLD outputs a standard analog test signal, injecting it into the front end of the current and voltage sampling channels. It then reads the test signal reading returned by the ADC and compares it with a preset standard value. If the deviation exceeds the allowable range, the corresponding sensor is flagged as faulty, and the system automatically switches to the backup sampling channel, simultaneously triggering an alarm signal to notify maintenance personnel. In drive power monitoring, the CPLD monitors the auxiliary power supply voltage of the IGBT driver board via the ADC, comparing the real-time monitored value with the standard voltage value. If the deviation exceeds the standard value... If the value is 5%, it is judged as an abnormal drive power supply. The PWM output is immediately blocked to prevent the abnormal power supply from damaging the IGBT, and the corresponding power fault code is recorded. In the CPLD logic self-test, the CPLD runs the built-in BIST logic, sends preset test vectors to the internal registers, state machine and memory, and then compares whether the actual output is consistent with the expected output to verify the integrity of the internal logic function. All self-diagnostic results and recovery operations are recorded in the CPLD's internal non-volatile memory and will not be lost even if the system is powered off. At the same time, this information is uploaded to the host computer in real time through the communication interface for maintenance personnel to perform fault analysis, root cause location and predictive maintenance. When the fault is eliminated, the CPLD can release the PWM block according to the host computer's instructions and restore the system to normal operation.

[0054] In summary, this embodiment fully realizes the dynamic monitoring and protection function of IGBT short-circuit current driven by CPLD through five consecutive stages, such as... Figure 1 As shown, the synchronous data acquisition in stage S100 provides accurate raw data for subsequent processes; the dynamic threshold calculation in stage S200 enables the short-circuit judgment benchmark to adapt to changes in operating conditions, avoiding misjudgment and insufficient protection; the dual-condition judgment mechanism in stage S300 ensures the accuracy of short-circuit state identification; the hardware-level fast protection operation in stage S400 effectively reduces the risk of IGBT damage; and the fault recording and self-diagnosis in stage S500 provide support for system maintenance and recovery. The entire method combines the high-speed hardware response characteristics of CPLD with dynamic algorithms, significantly improving the reliability and adaptability of IGBT short-circuit protection, and can be widely used in high-power power electronic systems such as new energy and industrial drives.

[0055] Example 2

[0056] like Figure 1 As shown in the figure, this embodiment provides the specific process of dynamic monitoring of IGBT short-circuit current by a CPLD-driven IGBT short-circuit current monitoring system. The steps of the specific process are as follows:

[0057] (1) System power-on and initialization

[0058] The system is powered on, and the CPLD main control module starts up.

[0059] The CPLD loads preset parameters and initializes the internal state machine, ADC control logic, and communication interface.

[0060] The sampling clock is activated, and the system enters the real-time monitoring ready state.

[0061] (2) Synchronous data acquisition

[0062] The CPLD sends a synchronous sampling signal.

[0063] Multi-channel ADC simultaneously acquires three key signals:

[0064] Channel 1: Acquires the signal output from the current sensor, converts it into a digital value, and obtains the collector current.

[0065] Channel 2: Acquires the signal isolated by the high-voltage differential probe, converts it into a digital value, and obtains the collector-emitter voltage.

[0066] Channel 3: Acquire the signal after the DC bus voltage divider is applied, convert it into a digital value, and obtain the DC bus voltage.

[0067] The temperature monitoring module synchronously collects the junction temperature of the IGBT.

[0068] (3) Data preprocessing and temporary storage

[0069] The CPLD stores the acquired collector current, collector-emitter voltage, and IGBT junction temperature data into its internal double-buffer RAM area.

[0070] CPLD calculates the voltage change rate at the current sampling point in real time.

[0071] (4) Calculation of dynamic protection threshold

[0072] CPLD invokes the built-in dynamic threshold algorithm.

[0073] The DC bus voltage and junction temperature are collected in real time as input parameters.

[0074] The CPLD calculates the applicable, adaptive short-circuit current judgment threshold under the current operating conditions.

[0075] (5) Short circuit condition judgment

[0076] Preset conditions: If the collector current collected in real time is greater than the dynamic threshold, and the voltage change rate is greater than the preset voltage change rate threshold, then the IGBT is determined to be in a short circuit state.

[0077] (6) Implement fast protection

[0078] Once the short circuit condition is confirmed, the CPLD will take immediate action.

[0079] The CPLD bypasses the main control DSP and directly sends soft shutdown command signals to the IGBT drive and protection circuit.

[0080] (7) Soft shutdown of drive circuit

[0081] After receiving the shutdown command, the drive circuit initiates a soft shutdown sequence.

[0082] By controlling the gate resistance, the voltage applied to the IGBT gate is slowly reduced from +15V to -8V, achieving soft turn-off and suppressing turn-off overvoltage.

[0083] (8) Record and report fault data

[0084] While the protection action is in progress, the CPLD records information about the fault, including: the timestamp of the fault occurrence, the fault type, and the electrical parameters at the moment the fault occurred.

[0085] The CPLD uploads the complete fault data packet to the main control DSP or host computer through the communication interface module.

[0086] (9) Start system self-diagnosis

[0087] During fault handling intervals or at fixed intervals, the CPLD initiates a self-diagnostic program.

[0088] Sensor calibration: The CPLD injects a standard test signal into the sampling channel to verify the accuracy of the ADC reading and determine whether the sensor is malfunctioning.

[0089] Power supply monitoring: Check if the power supply voltage of the driver board is within the normal range.

[0090] Logic self-test: Runs the built-in self-test logic to verify the completeness of the CPLD's own functions.

[0091] (10) System recovery preparation

[0092] Based on the self-diagnostic results and the type of fault, the system determines the recovery strategy.

[0093] If the fault is transient and the self-diagnosis is normal, the system can automatically reset or wait for instructions to reset and prepare to be put back into operation.

[0094] If a hardware fault is detected, the system remains locked and a maintenance request is submitted, awaiting manual intervention.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for dynamic monitoring of short-circuit current of IGBT driven by a CPLD, characterized in that, The specific steps of this method are as follows: S100 Real-time Data Acquisition: The data acquisition module controlled by the CPLD acquires the collector current flowing through the IGBT in real time. Collector-emitter voltage of IGBT and the junction temperature of IGBT ; S200, Dynamic Threshold Calculation: The CPLD is based on the real-time acquired DC bus voltage. and the junction temperature of the IGBT Dynamically calculate and adjust the short-circuit current judgment threshold. ; S300, Short-circuit condition judgment: The CPLD will collect the collector current in real time. With the dynamic short-circuit current threshold Compare and simultaneously analyze the collector-emitter voltage. rate of change When preset conditions are met, the IGBT is determined to be in a short-circuit state; S400, Fast Protection Execution: After determining that a short circuit is detected, the CPLD directly generates and outputs a turn-off signal to the IGBT drive circuit to force the IGBT to perform a soft turn-off operation. S500, Fault Data Recording and Uploading: The CPLD records the timestamp of the short-circuit fault, the fault type, and the key electrical parameters at the time of the fault. It uploads the fault data through the communication interface and initiates self-diagnosis and recovery.

2. The method for dynamic monitoring of IGBT short-circuit current driven by CPLD according to claim 1, characterized in that, In step S100, the specific steps for real-time data acquisition are as follows: The CPLD has a built-in fixed-frequency 500kHz sampling clock. The CPLD controls a multi-channel analog-to-digital converter to synchronously acquire data via a parallel bus. , and The first channel acquires the analog voltage signal output by the current sensor, and the second channel acquires the signal after isolation by the high-voltage differential probe. The signal, acquired via the third channel after voltage division from the DC bus, is... Signal; The CPLD internally allocates a double-buffered RAM area for temporarily storing sampled data and calculating the current differential value at each sampling point in real time. and voltage change rate This is used for subsequent short-circuit detection, reducing the computational burden on the main control DSP.

3. The method for dynamic monitoring of IGBT short-circuit current driven by CPLD according to claim 1, characterized in that, In step S200, the CPLD calculates the threshold for judging the short-circuit current through multi-parameter coupling. ,in, It is a dynamically calculated short-circuit current threshold, which serves as a benchmark value for real-time judgment of short-circuit conditions. It is the reference short-circuit current threshold under rated operating conditions, corresponding to the maximum permissible short-circuit current at rated DC voltage and rated junction temperature. This is the rated DC bus voltage, with a default value of 1050V-1400V. The DC bus voltage is collected in real time, sampled by a voltage sensor, converted by an analog-to-digital converter, and then input to the CPLD. This is a voltage correction factor, ranging from 0.8 to 1.2, used to characterize the effect of DC voltage on the IGBT's saturation voltage drop and short-circuit capability. For real-time monitoring of IGBT junction temperature, This is the rated operating junction temperature of the IGBT, with a default value of 125°C-150°C.

4. The method for dynamic monitoring of IGBT short-circuit current driven by CPLD according to claim 1, characterized in that, In S300, the preset condition for the short circuit state is: when When it enters a short circuit state, among which, It is a preset voltage change rate threshold. for rate of change and , This represents the collector-emitter voltage at the current sampling moment. This represents the voltage at the previous sampling time. The sampling interval is denoted as .

5. The method for dynamic monitoring of IGBT short-circuit current driven by CPLD according to claim 1, characterized in that, In S500, the self-diagnosis and recovery process is as follows: A self-test trigger pulse is generated by the CPLD to initiate a comprehensive self-diagnostic sequence, which includes sensor path verification, drive power monitoring and CPLD logic self-test. For sensor path verification: The CPLD outputs a standard analog test signal and injects it into the front end of the current and voltage sampling channels to check whether the reading returned by the ADC is within the error range. If the deviation exceeds the limit, the sensor is marked as faulty and the backup channel is switched to trigger an alarm. For drive power monitoring: The CPLD monitors the auxiliary power supply voltage of the IGBT driver board through the analog-to-digital converter. When the voltage value exceeds the standard value by 5%, it is judged that the drive power supply is abnormal, the PWM output is immediately blocked and the power fault code is recorded. For CPLD logic self-testing: The CPLD runs the built-in BIST logic to test the integrity of the internal registers, state machine and memory. By comparing the test vectors and expected outputs, the normal logic function is verified. Status reporting mechanism: All self-diagnostic results and recovery operations are recorded in memory and uploaded in real time via a communication interface for operation and maintenance analysis and predictive maintenance.

6. A CPLD-driven IGBT short-circuit current dynamic monitoring system, applicable to the CPLD-driven IGBT short-circuit current dynamic monitoring method according to any one of claims 1-6, characterized in that, The system comprises: The CPLD main control module, as the system's logic processing unit, internally implements functions including ADC control, dynamic threshold calculation, short-circuit state judgment state machine, and protection signal generation through hardware description language programming. The multi-parameter sampling module, connected to the CPLD main control module, is used to acquire the collector current of the IGBT. Collector-emitter voltage and DC bus voltage ; The temperature monitoring module, connected to the CPLD main control module, is used to monitor the junction temperature of the IGBT in real time. ; The IGBT drive and protection circuit is connected to the CPLD main control module and the gate of the IGBT. It is used to receive the normal PWM signal and the shutdown protection signal sent by the CPLD, and drive the IGBT to perform the corresponding switching action. The communication interface module is connected to the CPLD main control module and is used to realize data interaction between the CPLD main control module and the external main control DSP or host computer.

7. The CPLD-driven IGBT short-circuit current dynamic monitoring system according to claim 6, characterized in that, The working process of the IGBT drive and protection circuit is as follows: Driver chip: IGBT driver chip is used to provide isolation, amplification and protection functions. The operating voltage is +15V / -8V and the peak output current is ≥10A. Soft shutdown circuit design: After receiving the protection signal from the CPLD, the drive circuit starts the soft shutdown sequence, which reduces the gate voltage from +15V to -8V through a controllable gate resistor network. Active clamping unit: The circuit integrates active clamping function, which is achieved through a TVS diode and a feedback loop when... When the preset clamping voltage exceeds 1200V, current is automatically injected into the gate; Status feedback mechanism: The drive circuit monitors the saturation voltage drop and gate state of the IGBT in real time and feeds these status signals back to the CPLD through optocoupler isolation.

8. The CPLD-driven IGBT short-circuit current dynamic monitoring system according to claim 6, characterized in that, The communication interface module includes: Physical layer interface: Provides a variety of physical interface options, including high-speed fiber optic interface, CAN bus interface and SPI serial interface; Protocol stack architecture: The CPLD has a built-in communication protocol stack, including physical layer encoding / decoding, data link layer frame verification, and application layer message parsing. The application layer message is defined as: header byte, command word, data field, and tail byte. Configuration and diagnostic functions: Through the communication interface, the host computer can remotely configure the parameters of the CPLD and read the system self-diagnostic logs to achieve remote monitoring and maintenance; Redundancy design: The communication link supports dual redundancy mode. When the primary channel fails, it automatically switches to the backup channel, and all communication data is backed up and stored in the CPLD.

Images